Hi Alex
I encountered the same challenge as you, because i wanted to import the premise-transformed database to openlca.
to my understanding, it seems that ecoinvent uses some special "protocol" to generate their ecospold2 files, which they keep as a business secret. I have been unable to find any kind of workarounds. My solution is simply to use activity browser as LCA software. This of course implies learning a new software, as well as some migration challenges for old product systems and datasets from other softwares. Nonetheless, i believe activity-browser is superior to openlca as well as simapro (the lca software i know).
Hope my comment helps you. By the way, if you find other solutions to the database export, please get in touch with me :-)
Best
Simon